[RE-wrenches] grid-tie inverters & generators

Drake Chamberlin drake.chamberlin at redwoodalliance.org
Thu Nov 20 07:41:12 PST 2008


Talking to SMA, during a 4248 Sunny Island installation, w/ AC 
coupled Sunny Boys and a generator backup via transfer switch, I was 
told that backfeed to the generator needed to be addressed.  The 
Sunny Island has a setting that will limit backfeed to the generator 
to a value that can be set by the installer.  The setup requires that 
a relay in the transfer switch or generator close when the generator 
is on, to send a signal to the Island.  I was told that backfeed had 
to be set to less than 100 watts.

SMA tech support also reported that a number of generator control 
boards have been fried by inverters back feeding generators.

Drake

At 08:28 PM 11/19/2008, you wrote:
>In a message dated 11/19/2008 5:25:30 PM Pacific Standard Time, 
>kelly at whidbeysunwind.com writes:
>I can imagine, if the inverter tries to sync with the inverter, that 
>the voltage could rise, causing the inverter to disconnect, wait 5 
>minutes, repeat. Is there anything nasty that could happen?
>
>
>
>Kelly, That is the way I see it. I have tested systems with gens and 
>had no issues. The Sunny Boy would not boot to a gen 
>source.  However, you can understand what the official position must 
>be. There exist gensets with accuracy or it might just happen by 
>chance. Low probability, but not zero.
>
>Don Loweburg
>
>
>
>
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Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
740-448-7328
740-856-9648  
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